Surfaces which are in `z' or implicit form can often be rewritten in parametric form and pictures obtained using the parametric form are usually better. In addition, many surfaces can only be written in parametric form. Surfaces in parametric form are given as
e.g. the ellipsoid 
can be rewritten in parametric
form using `pseudo' spherical coordinates u,v
which is plotted using
plot3d( [ 2*cos(u)*sin(v), 3*cos(u)*sin(v), 2*sqrt(2)*cos(v)], Line Feed
u=0..2*Pi, v=0..Pi );
From Axes choose Boxed and then rotate the picture to get a better
view. Compare this with the picture obtained using implicitplot3d.
Also, notice the axes are divided but not labeled - can you point out
the x, the y, and the z axes?
The parametric form of the cone 
is obtained by rewriting
it in cylindrical coordinates as 
i.e. 
where r is
non-negative. So one of its parametric forms is
Now plot this as shown above - remember the Maple command for absolute
value is abs. The above surface may also be plotted using
the commands cylinderplot or sphereplot in the plots
package. Use Maple's help facility for more details.